#include<stdio.h>
int main()
{
	double result=0.0;
	int flag=1;
	for(int i=1;i<=100;i++)
	{
		result+=flag*(1.0/i);
		flag=-flag;
	}
	printf("1/1-1/2+1/3-1/4+1/5+...+1/99-1/100=%.3f\n",result);
	return 0;
}
